Direct measurements of the electric potential φ, using the Heavy Ion Beam Probing, have been undertaken in the T-10 tokamak, and in the helical devices with various magnetic topology: TJ-II, CHS and LHD. L-mode plasmas were considered. Despite the large differences in machine sizes, heating methods and the topology of the magnetic field, the observed φ shows the striking similarities: (i) Similar magnitudes of Er; (ii) For low densities, ne (0.5-1)× 1019 m−3, both φ and Er tends to be negative despite the use of different heating methods: Ohmic and ECR heating in T-10, ECRH and/or NBI in TJ-II, CHS and LHD; (iv) Application of ECRH, causing a rise in Te, results in more positive values for φ and Er. The analysis show that the main features of the φ dependences on the ne and Te agree with neoclassical predictions on the four devices within experimental and simulation precisions.